Trends in the Prevalence of Overweight and Obesity among Chinese School-Age Children and Adolescents from 2010 to 2015

Abstract

Background:

In China, recent rapid economic growth has been associated with increasing prevalence of childhood obesity. This study aimed to provide the most updated prevalence and trends in overweight and obesity among school-age children and adolescents in Shanghai, China, in 2010–2015.

Methods:

Annual physical examination data were collected from 66,410, 43,812, 104,887, 113,667, 119,401, and 109,068 school children and adolescents aged 6–17 in Minhang District, Shanghai, in 2010–2015. The outcome of interest was the prevalence of overweight and obesity based on the body mass index (BMI) criteria from the International Obesity Task Force.

Results:

In 2010–2015, the age-adjusted prevalence of overweight and obesity among boys increased from 21.2% to 31.7% and from 10.6% to 16.9% among girls. In 2015, the prevalence of obesity among boys was 9.3% higher than among girls (3.5%). The prevalence for boys was consistently higher than that for girls at each age and across years. The prevalence of overweight and obesity was highest at 11 years: 37.3% for boys and 19.8% for girls.

Conclusions:

The prevalence of overweight and obesity among Chinese urban children and adolescents is comparable to that in developed countries and was still increasing in 2010–2015. The prevalence among boys was alarmingly high. The findings highlight the need to develop public intervention strategies targeting urban children to stop the increasing trend in childhood obesity in China.

Introduction

Overweight and obesity represent a growing global public health concern in the 21st century.¹ Overweight and obesity have attracted much attention in the pediatric population in particular, because childhood and adolescence are critical developmental periods for future adult health. Overweight/obesity at this stage has been linked to many problems such as increased coronary heart disease risk, metabolic syndromes, psychological disorders, and behavioral comorbidities like attention-deficit/hyperactivity disorder.^2,3 In addition, overweight/obesity during childhood and adolescence is known to track into adulthood, so it is a critical time period to consider implementation of prevention efforts to stem the overweight/obesity epidemic.⁴

Following rapid economic development since the 1980 s, China has a rapidly increasing prevalence of overweight and obesity among children and adolescents.⁵ A recent (2013) study from Chinese National Surveys on Students Constitution and Health showed that the prevalence of obesity among children and adolescents aged 7–18 years increased from 0.2% in 1985 to 8.1% in 2010, and another meta-analysis also showed that the prevalence increased from 0.4% in 1981–1985 to 7.5% in 2006–2010.^6,7 While these studies provided some updated health information for obesity among Chinese children and adolescents, little is known about the continuation of those trends in the years after 2010. Moreover, there is little detailed information on the body mass index (BMI) growth of Chinese children and adolescents with increasing age, which is crucial for understanding the timing of the “takeoff” toward unhealthy BMI increase. Extensive studies have been conducted on the growth of children and adolescents in the United States as well as many other developed and developing countries, but the differences among populations can be substantial.^8–10 Thus, detailed studies on the Chinese population are necessary to better understand child growth and develop corresponding, population-specific overweight/obesity prevention strategies.

The purpose of this study is to provide the most updated prevalence estimates of overweight and obesity among school children and adolescents aged 6–17 years in Shanghai, China, and to examine the trends in prevalence between 2010 and 2015.

Subjects and Methods

The study was approved by the Ethics Committee of the School of Public Health and Nursing affiliated with Shanghai Jiao Tong University School of Medicine. Data were collected based on annual physical examinations among school children and adolescents in Minhang district, Shanghai, from 2010 to 2015. Shanghai is one of the four direct-controlled municipalities and the largest coastal city in China, with a population of more than 24 million as of 2015.¹¹ Minhang district has a land area of 143.15 square miles and a population of 2.54 million as of 2015.¹¹ Its level of economic development is comparable to other middle-sized cities in China.¹¹

In Shanghai, school children take physical examinations every year. Physicians or advanced practice registered nurses from community health centers brought physical examination instruments to each school for 1 day to take physical measurements of students. In Minhang District, there are 13 administrative divisions in total, and each has a community health center to perform physical examinations for the schools within the division. Physical examinations were supervised by Shanghai Minhang District Center for Disease Control and Prevention. Before physical examinations, schools informed parents about the examination and then parents gave consent to participate. On the examination day, minimal students missed the physical examinations due to sick leave or personal leave. In 2015, 109 068 individuals from 133 schools participated in the study. It covered 79.3% of total individuals aged between 6 and 17 years in Minhang District, compared with 86.1% in 2014, 84.1% in 2013, 82.3% in 2012, 36.4% in 2011, and 57.5% in 2010. During the physical examination, height and weight were measured without shoes and in light clothing. Standing height was measured to the nearest 0.1 cm using a stadiometer, and weight was measured to the nearest 0.01 kg using a digital scale. The digital scale was Tanita BC-420, and the stadiometer was SG-210 manufactured by Nantong Yuejian Physical Fitness Equipment Limited Company. Each individual was assigned a unique identifier associated with personal information and physical examination records.

Weight status was defined based on BMI, which is calculated as weight (in kilograms) divided by the square of height (in meters). The age- and sex-specific BMI cutoffs by the International Obesity Task Force (IOTF) were chosen to assess the weight status of each individual, since cutoffs were developed based on data from six countries, including China (Hong Kong).¹² In the IOTF criteria, the child centiles that are linked to BMI values at 25 and 30 for adults are considered the cutoff points for overweight and obesity.¹² To allow other researchers using different references to compare prevalence, we also applied the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) criteria to assess weight status.^13–15 We also applied a local reference from the Working Group on Obesity in China (WGOC) to make it easier to compare with other Chinese studies.¹⁶ The corresponding prevalence results are presented in Supplementary Table S1 (Supplementary data are available online at www.liebertpub.com/chi). In the subsequent analysis, such as comparing differences in the prevalence of overweight and obesity by year, IOTF criteria were chosen because they were generated based on data from six countries, including China, and were widely used in Chinese studies.

For individuals surveyed in 2010–2015, we compared year differences based on age-adjusted prevalence, which was calculated based on the age distribution in the Sixth National Population Census of China to control for possible age distribution differences across years.¹⁷ The combined prevalence of overweight and obesity was calculated by gender and age groups for year 2010 and 2015. The confidence interval for prevalence was constructed based on logit transformation.¹⁸ Chi-square tests were used to assess the year difference in the gender- and age-specific prevalence. To study the temporal trend in the prevalence, we also fitted two logistic regression models, one with overweight (including obesity) as the outcome, and one with obesity as the outcome. We used gender, age, and year as covariates, and we treated age as a categorical variable as the association between age and prevalence is non-linear. We also calculated the prevalence ratio between boys and girls in different age groups to study gender differences, and the confidence intervals were constructed based on log transformation. The logistic models were fitted using SAS (Version 9.4) and all the other statistical analyses were performed using R (Version R-3.3.2).

Results

The total sample sizes varied from 66,410 to 109,068 between 2010 and 2015. The sample sizes by year and by gender are shown in Table 1. In each year, the number of boys is slightly higher than the number of girls: the proportion of boys was 52.7% in 2010, 52.0% in 2011, 53.6% in 2012, 53.0% in 2013, 52.6% in 2014, and 52.6% in 2015.

Table 1.

Sample Size and Age-Adjusted Prevalence of Obesity and Overweight for Boys and Girls Aged 6–17 in Minhang District, Shanghai: 2010–2015

		Boys				Girls
Year of survey	N	OB (%)	OV (%)	OB+OV (%)	N	OB (%)	OV (%)	OB+OV (%)
2010	35710	5.5	15.7	21.2	32310	1.8	8.8	10.6
2011	22845	7.5	19.8	27.3	21083	2.4	11.2	13.6
2012	56336	8.3	20.4	28.8	48817	2.5	12.4	14.9
2013	68586	9.1	21.1	30.1	61244	2.8	13.3	16.1
2014	62997	8.8	21.2	30.1	56695	2.9	13.4	16.2
2015	56499	9.4	22.3	31.7	51088	3.2	13.7	16.9

OV, overweight; OB, obesity.

Based on the IOTF criteria, the temporal trend in the age-adjusted prevalence of overweight and obesity from 2010 to 2015 is shown in Table 1. Over the 6 years included in the study, there was an increasing trend in the overall prevalence of overweight and obesity among Shanghai Minhang children and adolescents. The age-adjusted prevalence of overweight for boys was 15.7% in 2010, and it gradually increased to 19.8% in 2011, 20.4% in 2012, 21.1% in 2013, 21.2% in 2014, and 22.3% in 2015. Meanwhile, age-adjusted prevalence of overweight among girls increased from 8.8% in 2010 to 11.2% in 2011, 12.4% in 2012, 13.3% in 2013, 13.4% in 2014, and 13.7% in 2015. Likewise, the age-adjusted prevalence of obesity for boys increased from 5.5% in 2010 to 9.4% in 2015, and that for girls increased from 1.8% to 3.2%.

In 2015, the combined prevalence of overweight and obesity was 31.8% among boys, much higher than 18.0% among girls ( \documentclass{aastex}\usepackage{amsbsy}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{bm}\usepackage{mathrsfs}\usepackage{pifont}\usepackage{stmaryrd}\usepackage{textcomp}\usepackage{portland, xspace}\usepackage{amsmath, amsxtra}\usepackage{upgreek}\pagestyle{empty}\DeclareMathSizes{10}{9}{7}{6}\begin{document} $$\chi^{2}$$ \end{document} = 2707.260, p < 0.001), according to IOTF criteria (Table 2). The prevalence of obesity was 9.3% among boys, also much higher than 3.5% among girls ( \documentclass{aastex}\usepackage{amsbsy}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{bm}\usepackage{mathrsfs}\usepackage{pifont}\usepackage{stmaryrd}\usepackage{textcomp}\usepackage{portland, xspace}\usepackage{amsmath, amsxtra}\usepackage{upgreek}\pagestyle{empty}\DeclareMathSizes{10}{9}{7}{6}\begin{document} $$\chi^{2}$$ \end{document} = 1475.144, p < 0.001). Overall, the prevalence of obesity in the younger age group, 6–11 years (boys 9.4%, girls 3.6%), is slightly higher than that in the older age group, 12–17 years (boys 8.7%, \documentclass{aastex}\usepackage{amsbsy}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{bm}\usepackage{mathrsfs}\usepackage{pifont}\usepackage{stmaryrd}\usepackage{textcomp}\usepackage{portland, xspace}\usepackage{amsmath, amsxtra}\usepackage{upgreek}\pagestyle{empty}\DeclareMathSizes{10}{9}{7}{6}\begin{document} $$\chi^{2}$$ \end{document} = 5.739, p < 0.05; girls 3.1%, \documentclass{aastex}\usepackage{amsbsy}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{bm}\usepackage{mathrsfs}\usepackage{pifont}\usepackage{stmaryrd}\usepackage{textcomp}\usepackage{portland, xspace}\usepackage{amsmath, amsxtra}\usepackage{upgreek}\pagestyle{empty}\DeclareMathSizes{10}{9}{7}{6}\begin{document} $$\chi^{2}$$ \end{document} = 6.929, p < 0.01). To allow comparison with other published studies, we also applied different overweight/obesity references and calculate prevalence (Supplementary Table S1). Based on the CDC criteria, the prevalence was 34.8% among boys and 17.4% among girls. Based on the WGOC criteria, it was 37.4% among boys and 21.1% among girls. Based on the WHO criteria, we obtained much higher prevalence: 44.9% among boys and 22.9% among girls. The prevalence ratio comparing boys to girls is 1.8 for overweight and obesity combined, 1.6 for overweight alone, and 2.6 for obesity alone (Table 2), showing that there are substantial gender differences and the prevalence among boys is consistently much higher than girls.

Table 2.

The Prevalence of Overweight and Obesity, Overweight Alone, and Obesity Alone by Gender and Age Groups Based on IOTF Criteria: 2015

	Prevalence% (95% CI)
Status/Age	Boys	Girls
Overweight and obesity
All participants	31.8 (31.4–32.2)^*	18.0 (17.7–18.3)
6–11	31.7 (31.3–32.1)^*	18.2 (17.8–18.6)
12–17	32.0 (31.2–32.8)^*	17.4 (16.7–18.1)
Overweight
All participants	22.5 (22.2–22.8)^*	14.5 (14.3–14.8)
6–11	22.3 (21.9–22.7)^*	14.6 (14.2–15.0)
12–17	23.3 (22.6–24.0)^*	14.3 (13.7–14.9)
Obesity
All participants	9.3 (9.1–9.5)^*	3.5 (3.3–3.7)
6–11	9.4 (9.1–9.7)^{* a}	3.6 (3.4–3.8)^b
12–17	8.7 (8.2–9.2)^*	3.1 (2.8–3.4)

p < 0.001, Chi-square test indicated significant difference between boys and girls in the same age groups.

p < 0.05, Chi-square test indicated significant difference between different age group.

p < 0.01, Chi-square test indicated significant difference between different age groups.

The detailed age-specific prevalence of overweight and obesity by gender in year 2010 and 2015 is shown in Table 3, and chi-square tests comparing year difference reached statistical significance, p < 0.05. The prevalence of overweight and obesity for boys is much higher than that for girls across all ages. For boys, the prevalence of overweight and obesity combined peaked at 37.3% at the age of 11 in 2015, the same as girls whose prevalence (19.8%) also peaked at the age of 11 in 2015. After 11, the prevalence fell gradually as age increased. Overall, boys and girls exhibited the highest prevalence of overweight and obesity at 9–13 years, after which the prevalence dropped as age increased.

Table 3.

Gender- and Age-Specific Prevalence of Overweight and Obesity for Children and Adolescents Aged 6–17 in Minhang District, Shanghai, Based on IOTF Criteria: 2010 and 2015

	Prevalence (%, 95% CI)
Year	2010	2015
Boys
6	22.2 (20.2–24.2)	24.8 (23.8–25.8)^*
7	22.1 (20.9–23.3)	27.1 (26.1–28.1)^*
8	20.2 (19.1–21.3)	30.9 (29.9–31.8)^*
9	16.4 (15.3–17.5)	34.3 (33.3–35.4)^*
10	18.7 (17.5–19.9)	36.0 (34.9–37.1)^*
11	25.8 (24.4–27.2)	37.3 (36.1–38.4)^*
12	26.8 (25.2–28.4)	35.2 (33.7–36.7)^*
13	24.0 (22.5–25.5)	32.2 (30.8–33.6)^*
14	20.3 (18.8–21.8)	28.9 (26.6–31.2)^*
15	18.8 (16.9–20.7)	29.7 (27.1–32.3)^*
16	17.8 (15.5–20.1)	27.8 (25.5–30.0)^*
17	18.0 (15.4–20.6)	26.2 (22.5–29.9)^*
Total	21.2 (20.8–21.6)	31.8 (31.4–32.2)^*
Girls
6	13.2 (11.5–14.9)	16.9 (15.9–17.8)^*
7	12.7 (11.7–13.7)	17.2 (16.3–18.1)^*
8	11.3 (10.3–12.3)	17.5 (16.7–18.3)^*
9	8.9 (8.0–9.8)	18.7 (17.8–19.7)^*
10	9.7 (8.8–10.6)	19.4 (18.4–20.4)^*
11	12.6 (11.4–13.8)	19.8 (18.8–20.8)^*
12	13.6 (12.3–14.9)	18.6 (17.3–19.9)^*
13	10.1 (9.0–11.2)	19.5 (18.2–20.7)^*
14	8.60 (7.5–9.7)	17.6 (15.6–19.7)^*
15	9.4 (8.0–10.8)	12.3 (10.5–14.2)^*
16	9.8 (8.1–11.5)	14.8 (13.1–16.5)^*
17	8.7 (6.8–10.6)	14.1 (11.3–16.9)^*
Total	10.8 (10.5–11.1)	18.0 (17.7–18.3)^*

p < 0.05, Chi-square test indicated significant difference between 2010 and 2015.

The gender differences and temporal trends in the prevalence of overweight and obesity were further investigated in logistic models (Table 4). After controlling for age and year, the estimated odds of overweight (including obesity) and that of obesity for boys were more than twice the odds for girls, respectively. After controlling for gender and age, the logistic model results also show that in 2010–2015, the odds of overweight and obesity were estimated to increase 9% and 10% each year (p-values <0.001).

Table 4.

Logistic Regression Analysis Results Showing Gender Differences and Temporal Trends in Overweight and Obesity from 2010 to 2015

	Odds ratio	95% CI	p-value
Overweight (including obesity)
Gender
Boys vs. Girls	2.08	2.06–2.11	<0.001
Year
year x+1 vs. year x	1.09	1.09–1.10	<0.001
Obesity
Gender
Boys vs. Girls	2.78	2.71–2.85	<0.001
Year
year x+1 vs. year x	1.10	1.09–1.11	<0.001

The logistic models were fitted using age, gender, and year as covariates. The estimated odds ratio for age is not shown here, as the age-specific prevalence in Table 3 gives better reference for the nonlinear association of age with overweight and obesity.

Discussion

Our study provides the most recent prevalence estimates of overweight and obesity among Chinese urban children and adolescents, presenting data as recent as 2015. The prevalence of overweight and obesity among boys in our study appears as high as that in developed countries. In the analysis by the Global Burden of Disease (GBD) 2013, the prevalence of overweight and obesity among children and adolescents in developed countries in 2013 was reported to be 23.8% in boys based on IOTF criteria.¹⁹ In comparison, Shanghai boys in our study had a much higher prevalence, 31.7%. We also compared Shanghai boys with US Asian boys to control for possible ethnicity differences. In the recent publication for US children in 2012, among the non-Hispanic Asian population, the combined prevalence of overweight and obesity was 24.5% for boys aged 6–11 years and 33.9% for boys aged 12–19 years based on CDC criteria, both lower than 34.8% for Shanghai boys aged 6–17 years (Supplementary Table S1).⁹ If we focus on the prevalence of obesity specifically, it was 16.5% among Shanghai boys aged 6–17 years, also higher than the prevalence among US non-Hispanic Asian boys, 13.2% and 14.8% among 6–11 years and 12–19 years, respectively.⁹ The alarmingly high prevalence estimates in our study reveal an urgent need for preventative intervention among Chinese urban boys.

Compared with the high prevalence of overweight and obesity among boys, the prevalence among girls was consistently much lower at different ages and across years (Tables 1–3). Nevertheless, the prevalence among Shanghai girls also reached the same level as that in developed countries. For instance, in 2012, the combined prevalence of overweight and obesity among US non-Hispanic Asian girls was 14.9% and 15.0% among 6–11 years and 12–19 years, respectively.⁹ In comparison, the combined prevalence among Shanghai girls was 17.6% and 16.8% in 6–11 and 12–17 years using the same CDC criteria. The prevalence among Shanghai girls in 2015 was higher than that among US non-Hispanic Asian girls, reaching the same high level as that in the developed countries.

Comparing with other Chinese children studies, our estimated prevalence of overweight and obesity tends to be higher. In 2006, the China Health and Nutrition Survey (CHNS) gave estimated prevalence of overweight and obesity as 10.1% and 5.3% among boys and 6.4% and 4.6% among girls, respectively, using IOTF criteria.²⁰ Our estimated prevalence of obesity among Shanghai girls is lower, but all the other estimates are much higher than the ones in the national survey (Table 2). It is as expected, because Shanghai as one of the four municipalities has relatively high level of economic development, and the prevalence of overweight and obesity is higher due to high-energy/high-fat diets and more sedentary lifestyles.²¹

On the other hand, our study also gave higher prevalence than previously reported urban prevalence, suggesting an increase in recent years. For instance, in a Chinese study in 2005, the prevalence of overweight and obesity in north coastal big cities, including Beijing, Shanghai, and Tianjin, was reported as 32.5% among boys and 17.6% among girls using WGOC criteria.²² In comparison, our study gave an estimate of 37.4% among boys and 21.1% among girls, respectively. In 2006, CHNS also reported an estimated prevalence of overweight and obesity as 12.5% and 7.4% among urban boys and 7.4% and 5.7% among urban girls, respectively, using IOTF criteria.²⁰ Except for the prevalence of obesity among girls, these previously reported numbers are much lower than the estimates in our study, which confirms the increase in prevalence over recent years.

The prevalence of overweight and obesity among Shanghai children is higher than that in previous years, and it was still increasing in 2010–2015. The gender- and age-specific prevalence of overweight and obesity show increasing patterns in 2010–2015 (Tables 1 and 3), which confirm the global surge of obesity among developing countries in recent publications and also the increasing trends in recent obesity studies in China.^6,7,21,23 In the most recent article by Non-communicable Disease Risk Factor Collaboration on Lancet, it has been shown that the rise in mean BMI has accelerated in East Asia for both genders.²⁴ In our study, while the prevalence among girls was not as high as that among boys, it nevertheless showed the same increasing temporal trends over the 5 years. The prevalence of obesity among boys and among girls almost doubled over the 5 years, which suggests the increasing temporal trend among the whole child population and reveals the urgent situation among Chinese urban children.

We also examined the gender- and age-specific prevalence of overweight and obesity (Tables 2 and 3), and the prevalence of overweight and obesity among boys are consistently much higher than that among girls at different ages. The prevalence ratios comparing boys to girls are 1.6 for overweight alone and 2.6 for obesity alone (Table 2), showing substantial gender differences. In addition, the gender differences are approximately the same in the younger and the older age groups. This pattern is quite different from the global gender pattern reported in GBD 2013, where gender differences were small among children and adolescents.¹⁹ On the other hand, this pattern is the same as that among US non-Hispanic Asian children: for example, the combined prevalence of overweight and obesity for boys is 13.2% and 14.8% among 6–11 years and 12–19 years, both higher than 3.7% and 7.3% among girls.⁹ However, the situation is different among US non-Hispanic white children, as the prevalence of obesity for girls is higher than that for boys.⁹ This result suggests that gender differences in overweight and obesity are not the same among different populations.

In addition, we found that for both Shanghai girls and boys, the younger age group (6–11 years, primary school) generally had higher prevalence of obesity compared to the older age group (12–17 years, middle school). For instance, in 2015, the prevalence of obesity was 17.3% and 5.4% for boys and girls aged 6–11 years, higher than 14.0% and 4.5% for boys and girls aged 12–17 years, respectively, based on CDC criteria (Supplementary Table S1). However, the situation was different among US non-Hispanic Asian children, as it was 13.2% and 14.8% for boys and 3.7% and 7.3% for girls aged 6–11 years and 12–17 years, respectively.⁹ The same pattern holds for the combined prevalence of overweight and obesity. By further looking at each age-specific prevalence among Shanghai children, we found that it generally increased through 6–11 years, and then gradually decreased after 12 years. The prevalence of overweight and obesity for both boys and girls peaked at 9–13 years. This pattern is also different from that among US children, whether all races or non-Hispanic Asian alone, who showed higher prevalence in the older age group than that in the younger age group.⁹ Chinese children tend to have higher prevalence of obesity in the younger age group, while US children tend to have higher prevalence in the older age group, which may suggest different growth patterns or differences in the timing of the onset of puberty among different populations, and thus inform different intervention strategies.

The different patterns in the age-specific prevalence may be explained by the different growth patterns among different populations. For instance, the peak of height velocity was at 12.1 years among US girls and at 13.7 years among US boys.²⁵ In comparison, the peak height velocity was at 11 and 12 years in Singapore and at 10.5 and 12.5 years in Taipei, China.^26,27 In addition, based on radiographs to assess skeleton maturity, Asians mature sooner than African and white peers in the United States.²⁸ Thus, the earlier peak of BMI and prevalence of overweight and obesity among Shanghai children line up with the generally faster pace of growth in the population. This information provides valuable insights for Chinese policy makers involved in childhood obesity prevention, as it is important to develop prevention and intervention programs targeting the right age group. For both Chinese boys and girls, public intervention strategies should target the younger age group in primary school. Furthermore, because the prevalence of overweight and obesity peaked at 9–13 years, the target age group should be before 9 years so as to more effectively prevent the “takeoff” toward unhealthy BMI increase and control the high prevalence of overweight and obesity.

Prevention of childhood obesity is crucial for controlling adulthood obesity. A systematic review shows that around 55% of obese children are going to be obese in adolescence and 80% of obese adolescents continue to be obese in adulthood.²⁹ Our study shows an increasing trend in the prevalence of childhood overweight and obesity in China, and thus it is vital to control childhood obesity, thereby preventing the growing adulthood obesity burden. While high prevalence of childhood overweight and obesity has caught the government's attention, currently there is a lack of efficient intervention and prevention strategies. In the Plan for Healthy China 2030, the government calls for whole-population obesity intervention and childhood obesity intervention in particular, although detailed strategies have not been developed yet.³⁰ Based on current situation in China, our study calls for home- and school-based childhood obesity intervention strategies. At home, it is important to educate Chinese parents on childhood obesity issues and healthy diets and lifestyles, as Chinese parents do not pay much attention to childhood obesity and sometimes even mistake obesity for adequate nutrition. At school, physical education programs should be established to increase physical activity and decrease sedentary behaviors, as decreased physical activity and increased screen exposure are known to be associated with higher obesity risks among school children.³¹ Given the alarmingly high prevalence of overweight and obesity among boys, public health strategies can be tailored according to characteristics of boys to increase intervention efficiency. For instance, boys should be encouraged to decrease screen exposure and increase participation in team sports such as basketball and football to develop hobbies and sustainable healthy lifestyles.

Some limitations of the study should be noted when interpreting the results. First, due to the limited number of variables in the annual physical examination dataset, it does not contain socioeconomic information, such as family income and parent's educational attainment, or lifestyle information, such as physical activity and dietary habits, which are likely associated with childhood overweight and obesity. Our study provides the most updated prevalence and describes the increasing trends in childhood overweight and obesity in Shanghai, and future research should collect more information on demographics, lifestyles, and other risk factors to study the possible association with childhood obesity and identify the key factors associated with increased prevalence. Second, the physical examination data were collected from Shanghai, where the level of economic development is higher than rural areas in China. Thus, this study describes the current situation of overweight and obesity among urban children and adolescents, and it is expected that our study results gave higher prevalence than other national studies in China. On the other hand, as the economic development of Shanghai precedes other parts of China, our study also serves as a forecast for what may happen in other regions under economic development: an increase in the prevalence of overweight and obesity is likely to accompany economic growth. Therefore, our study initiates the call for effective intervention strategies to control the high prevalence of overweight and obesity in Shanghai and to prevent the increasing trend in other regions of China.

Conclusion

Our study shows that Chinese urban children and adolescents have high prevalence of overweight and obesity comparable to that in developed countries. Chinese boys have much higher prevalence than Chinese girls, and the prevalence was still increasing from 2010 to 2015. The younger primary school-aged group (6–11 years) had higher prevalence than the older age middle school-aged group (12–17 years). Thus, our findings are important to policy makers involved in childhood obesity control and prevention. Public intervention strategies should target children in primary school to combat the childhood and adolescence obesity epidemic in China.

Footnotes

Acknowledgments

The study was supported, in part, by the National Natural Science Foundation of China (Grant No.71303156) and Innovation Program of Shanghai Municipal Education Commission(Grant No. 14YS019). We thank Mengting Zhong, Xiaofan Ren, and Ziang Li, who are undergraduate students from Shanghai Jiao Tong University, for their help with data collection in the study.

Author Disclosure Statement

No competing financial interests exist.

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